Abstract: In regions of the world such as Eastern Europe and South-East Asia, the HIV pandemic is being driven by the spread of HIV within drug-abusing populations. As HIV infected individuals live longer with the success of CART, neurological complications are emerging as a significant health issue, particularly among HIV-infected drug abusers. HIV infected individuals who abuse methamphetamine and cocaine show a significant increase in the incidence and severity of neuropathology and in the development of HIV-associated neurological disorders (HAND). The mechanism(s) leading to the acceleration HAND remain unclear; however, both cocaine and methamphetamine act by increasing in extracellular levels of the neurotransmitter dopamine (DA) within the central nervous system (CNS). Our findings demonstrate that dopamine increases HIV replication in primary human macrophages, which are the primary target for HIV infection in the CNS. Our research showed that this increase in macrophage HIV replication is due, at least in part, to the infection of greater numbers of macrophages through the activation of a D2-like dopamine receptor. Additionally, studies in simian immunodeficiency virus infected rhesus macaques showed that increased extracellular dopamine enhances intracerebral HIV replication and exacerbates central nervous system pathology. Together, these studies indicate that the effects of dopamine on HIV infection of macrophages could be a common mechanism by which drug abuse exacerbates the development of HAND. Macrophages are the primary targets and sources of HIV in the CNS, as well as a major immune responder and a major source of cytokines and chemokines. Cytokines and chemokines increase neuroinflammation and mediate the recruitment of uninfected macrophages to sites of inflammation, enabling the virus to spread to uninfected macrophage populations. Our data show that dopamine not only increases HIV replication in macrophages, but it activates dopamine receptor mediated signaling, modulates activation of chemotatic proteins and alters cytokine production. These data suggest that drug-induced increases in dopamine would not only increase the extent of HIV infection in the CNS, but could also enhance the spread of HIV to uninfected macrophages and alter the macrophage response to infection. To characterize the mechanism(s) by which dopamine increases HIV infection in macrophages and alters macrophage immune function, we will define dopamine mediated changes in the HIV replication cycle in macrophages, examine alterations in macrophage chemotaxis and production of inflammatory cytokines/chemokines, and characterize the DR signaling pathways in macrophages mediating these functions. We hypothesize that dopamine increases HIV infection in macrophages and alters macrophage functions through activation of dopamine receptors and transporter, contributing to the exacerbated the development of HAND in HIV infected drug abusers.